Scheduling of variable area fan nozzle to optimize engine performance

Abstract

A disclosed control system for a gas turbine engine includes a controller configured to set a position of the variable area fan nozzle according to a predetermined schedule of variable area fan nozzle positions corresponding to a flight operating condition. The schedule is determined in view of a relationship between a position of the variable area nozzle and a performance level of the engine at current flight conditions.

What is claimed is: 
     
       1. A control system for a gas turbine engine comprising:
 a fan nacelle including variable area nozzle for regulating airflow through a bypass duct; 
 an actuator coupled to the variable area nozzle for regulating air flow by positioning the variable area nozzle; and 
 a controller configured to set a position of the variable area fan nozzle according to a predetermined schedule of variable area fan nozzle positions corresponding to a flight operating condition, wherein the flight operating condition includes an amount of bleed air demand into an environmental control system within an aircraft, wherein the predetermined schedule includes a plurality of variable area fan nozzle positions determined to produce a value of an engine performance parameter at the flight operating condition. 
 
     
     
       2. The control system as recited in  claim 1 , wherein the engine performance parameter comprises at least one of thrust and fuel consumption. 
     
     
       3. The control system as recited in  claim 1 , wherein predetermined schedule includes a plurality of variable area fan nozzle position determined in view of an engine operating constraint. 
     
     
       4. The control system as recited in  claim 3 , wherein the engine operating constraints include at least one of a shaft speed, turbine temperature and bleed system condition. 
     
     
       5. The control system as recited in  claim 1 , wherein the flight operating condition comprises one of an aircraft speed, an engine speed and a bleed system demand. 
     
     
       6. The control system as recited in  claim 5 , including operating the variable area fan nozzle according to the predetermined schedule of variable area fan nozzle positions at air speeds greater indicative of flight operations other than take-off and landing. 
     
     
       7. A method of defining a schedule of positions for a variable area fan nozzle of a gas turbine engine by a controller, the method comprising:
 constraining a characteristic of engine operation; 
 defining a relationship between a position of the variable area nozzle and a performance level of the engine with the constrained engine operating characteristic, wherein the constrained engine operating characteristic includes an amount of bleed air demand from an environmental control system of an aircraft; 
 relating the position of the variable area nozzle for the performance level of the engine to a flight condition; 
 defining a set of commands executable by a controller of the variable area fan nozzle for moving the variable area fan nozzle to the position related to the flight condition; 
 programming a controller to include the defined set of commands and to move the variable area fan nozzle to the position related to the performance level of the engine responsive to a flight condition; and defining a schedule of positions of the variable area fan nozzle that correspond with a plurality of values of the flight condition. 
 
     
     
       8. The method as recited in  claim 7 , wherein the flight condition includes at least one of an air speed, an engine speed and a bleed system condition and including moving the variable area fan nozzle to the defined position related to one of the air speed, engine speed and bleed system condition. 
     
     
       9. The method as recited in  claim 7 , including the step of defining the schedule of positions of the variable area fan nozzle that correspond with the plurality of values of the flight condition for each of a plurality of engine operation constraints. 
     
     
       10. The method as recited in  claim 9 , wherein the plurality of engine operation constraints includes at least one of an engine speed, engine temperature and bleed system condition. 
     
     
       11. The method as recited in  claim 7 , wherein the performance level of the engine comprises a performance of the engine with regard to at least one of a thrust delivery and a fuel consumption. 
     
     
       12. The method as recited in  claim 7 , wherein the variable area fan nozzle includes at least one flap movable relative to a fixed nacelle portion and moving the variable area fan nozzle include moving the flap a distance from the fixed nacelle portion. 
     
     
       13. The method as recited in  claim 7 , including defining a model representing responses of gas turbine engine operating characteristics relative to a position of a variable areas fan nozzle. 
     
     
       14. The method as recited in  claim 13 , including defining a relationship with the model between an engine operating characteristic and a position of the variable area fan nozzle.